Light sources incorporating light emitting diodes

ABSTRACT

Taught herein are various light sources using light emitting diodes. A light source includes a housing, a connector configured for connection to an electrical socket and coupled to an end of the housing, at least one organic light emitting diode sheet mounted inside the housing and in electrical communication with the connector, and a power supply circuit for supplying electrical current to the at least one organic light emitting diode through the connector.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a divisional of U.S. patent application Ser. No.12/242,033, filed Sep. 30, 2008, which is a continuation of Ser. No.11/007,417, filed Dec. 8, 2004, now U.S. Pat. No. 8,093,823, issued Jan.10, 2012, which is a continuation-in-part of U.S. patent applicationSer. No. 09/782,375, filed Feb. 12, 2001, now U.S. Pat. No. 7,049,761,issued May 23, 2006, which claims priority to provisional ApplicationSer. No. 60/181,744, filed Feb. 11, 2000.

FIELD OF THE DISCLOSURE

The present invention relates to light sources incorporating lightemitting diodes.

BACKGROUND

All lighting systems have shortcomings. Conventional fluorescentlighting systems include, for example, light sources such as fluorescentlight tubes and ballasts. Fluorescent lighting systems are used in avariety of locations, such as buildings and transit buses, for a varietyof lighting purposes, such as area lighting or backlighting. Suchsystems have some advantage over incandescent lighting systems, whichinclude light sources such as light bulbs incorporating filaments.Fluorescent lighting systems, for example, generate less heat. On theother hand, the light generated by fluorescent lighting systems is lessdesirable in many applications than incandescent lighting systemsbecause conventional fluorescent lighting systems generally produce acooler light that has more blue and less red than incandescent lightingsystems. Conventional fluorescent and incandescent lighting systems canalso include fragile components. Fluorescent light tubes, in particular,have a short life expectancy, are prone to fail when subjected toexcessive vibration, consume high amounts of power, require a highoperating voltage and include several electrical connections that reducereliability. Conventional ballasts are highly prone to fail whensubjected to excessive vibration.

BRIEF SUMMARY

The present invention includes replacements for conventional lightsources such as fluorescent light tubes and incandescent light bulbsthat overcome the disadvantages of the prior art. Specifically, theinvention comprises various light sources incorporating light emittingdiodes. Light emitting diodes can be manufactured that have superiorcolor rendering than most fluorescent lamps, which improves theusability and aesthetic qualities of the light. In addition, lightemitting diodes are less fragile than incandescent and fluorescentlighting components.

A first embodiment of the light source according to the presentinvention comprises a housing portion, a connector disposed at an end ofthe housing portion, at least one organic light emitting diode sheetsurrounded by at least a portion of the housing portion, the at leastone organic light emitting diode sheet in electrical communication withthe connector, and a power supply circuit for supplying electricalcurrent to the at least one organic light emitting diode sheet throughthe connector. The housing portion can comprise a rigid hollow bulb madeof glass or plastic, for example, or can comprise a clear or tintedpotting material or a thin conformal coating. The organic light emittingdiode sheet(s) can be flexible. Other variations of this embodiment arepossible and are described in more detail herein.

A second embodiment of the light source according to the presentinvention comprises a housing portion formed of a coating material, aconnector disposed at an end of the housing portion, a plurality oflight emitting diodes surrounded by the housing portion and mounted on acircuit board, the plurality of light emitting diodes electricallycoupled to the connector, and a power supply circuit for supplyingelectrical current to the plurality of light emitting diodes, the powersupply circuit electrically coupled to the connector. The coatingmaterial can be a clear or tinted potting material or can be a thinconformal coating for the circuit board and light emitting diodes. Atleast part of the power supply circuit can be mounted on the circuitboard. Other variations of this embodiment are also possible and aredescribed in more detail herein.

A second embodiment of the light source according to the presentinvention comprises a connector adapted to be coupled to an electricalsocket, a circuit board extending from the connector, at least one lightemitting diode mounted on the circuit board and in electricalcommunication with the connector, the at least one light emitting diodeexposed to an ambient environment external of the light source, and apower supply circuit for supplying electrical current to the at leastone light emitting diode through the connector.

Other embodiments are described in more detail herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 is a line drawing showing a light tube, in perspective view,which in accordance with the present invention is illuminated by LEDspackaged inside the light tube;

FIG. 2 is a perspective view of the LEDs mounted on a circuit board;

FIG. 3 is a cross-sectional view of FIG. 2 taken along lines 3-3 withthe addition of optional heat sinks;

FIG. 4 is a fragmentary, perspective view of one embodiment of thepresent invention showing one end of the light tube disconnected fromone end of a light tube socket;

FIG. 5 is an electrical block diagram of a first power supply circuitfor supplying current to power a light source incorporating LEDs;

FIG. 6 is an electrical schematic of a switching power supply typecurrent limiter;

FIG. 7 is an electrical block diagram of a second power supply circuitfor supplying current to power a light source incorporating LEDs;

FIG. 8 is an electrical block diagram of a third power supply circuitfor supplying current to power a light source incorporating LEDs;

FIG. 9 is a fragmentary, perspective view of a second embodiment of thepresent invention showing one end of a light tube disconnected from oneend of the light tube socket;

FIG. 10 is an electrical block diagram of a fourth power supply circuitfor supplying current to power a light source incorporating LEDs;

FIG. 11 is a fragmentary, perspective view similar to FIG. 4 showinganother embodiment of the circuit board;

FIG. 12 is a line drawing showing a light bulb, in perspective view,which in accordance with the present invention is illuminated by LEDspackaged inside the light bulb;

FIG. 13 is a cross-sectional view of FIG. 1 taken along lines 13-13;

FIG. 14 is a perspective view of a sheet comprising an organiclight-emitting diode that can be incorporated into the light sources ofthe present invention; and

FIG. 15 is an end view of a light tube omitting the end cap andelectronics and incorporating an organic light-emitting diode.

DETAILED DESCRIPTION

FIG. 1 is a perspective view showing a light source according to theinvention in the form of a light tube 20. In accordance with a firstembodiment of the invention, the light tube 20 is illuminated by LEDs 22packaged inside the light tube 20. The light tube 20 includes acylindrically shaped housing portion 24 having a pair of end caps 26 and28 disposed at opposite ends of the housing portion 24. Preferably, thehousing portion 24 is made from a transparent or translucent materialsuch as glass, plastic, or the like. As such, the housing material maybe either clear or frosted.

In a preferred embodiment of the present invention, the light tube 20has the same dimensions and end caps 26 and 28 (e.g., electrical malebi-pin connectors, type G13) as a conventional fluorescent light tube.As such, the present invention can be mounted in a conventionalfluorescent light tube socket 40 as shown in FIG. 4. FIG. 4 is afragmentary, perspective view of one embodiment of the present inventionshowing one end of the light tube 20 disconnected from one end of alight tube socket 40. Similar to conventional fluorescent lightingsystems and in this embodiment of the present invention, the light tubesocket 40 includes a pair of electrical female connectors 42 and thelight tube 20 includes a pair of mating electrical male connectors 44.

Alternatively, end caps with single-pin connectors, incorporatingso-called “instant start” ballasts, as well as recessed double-pinconnectors are also possible with suitable mounting sockets for thisembodiment. Another possible connector and its related socket for alight tube 20 are shown in FIG. 9. FIG. 12, discussed in more detailbelow, shows yet another connector in a different embodiment of thelight source according to the present invention. The light tube 20 couldalso be in the form of a conventional round housing portion, i.e., the“doughnut” shaped bulb, with the 4-pin connector used with such bulbs.

Returning now to FIG. 1, the line drawing of FIG. 1 also reveals theinternal components of the light tube 20. The light tube 20 furtherincludes a circuit board 30 with the LEDs 22 mounted thereon. Thecircuit board 30 and LEDs 22 are enclosed inside the housing portion 24and the end caps 26 and 28.

FIG. 2 is a perspective view of the LEDs 22 mounted on the circuit board30. A group of LEDs 22, as shown in FIG. 2, is commonly referred to as abank or array of LEDs. Within the scope of the present invention, thelight tube 20 may include one or more banks or arrays of LEDs 22 mountedon one or more circuit boards 30. In a preferred embodiment of thepresent invention, the LEDs 22 emit white light and, thus, are commonlyreferred to in the art as white LEDs. In FIGS. 1 and 2, the LEDs 22 aremounted to one surface 32 of the circuit board 30. In a preferredembodiment of the present invention, the LEDs 22 are arranged to emit orshine white light through only one side of the housing portion 24, thusdirecting the white light to a predetermined point of use. Thisarrangement reduces light losses due to imperfect reflection in aconventional lighting fixture. In alternative embodiments of the presentinvention, LEDs 22 may also be mounted, in any combination, to the othersurfaces 34, 36 and/or 38 of the circuit board 30.

FIG. 3 is a cross-sectional view of FIG. 2 taken along lines 3-3. Toprovide structural strength along the length of the light tube 20, thecircuit board 30 shown is designed with an H-shaped cross-section thatfits snugly into the light tube 20. To produce a predetermined radiationpattern or dispersion of light from the light tube 20, each LED 22 ismounted at an angle relative to adjacent LEDs and/or the mountingsurface 32. The total radiation pattern of light from the light tube 20is affected by (1) the mounting angle of the LEDs 22 and (2) theradiation pattern of light from each LED. Currently, white LEDs having aviewing range between 6° and 120° are commercially available. Note thatFIG. 3 includes optional heat sinks 35, not included in FIG. 2, whichextend from the side 34 of the circuit board 30 opposed to the LEDs 22.The addition of the heat sinks 35 may be desirable in certainenvironments and where a large number of LEDs 22 are incorporated. Theheat sinks 35 could be made of metal, ceramic or other heat dissipatingmaterials and, of course, could be incorporated in different numbers orconfigurations.

Although the circuit board 30 as shown is H-shaped as discussed above,other shapes for the circuit board 30 are possible. For example, thecircuit board 30 may be a conventional flat circuit board 30 as shown inFIG. 11. Note that the housing portion 24 has been omitted, and theplurality of LEDs 22 has been removed from FIG. 11 for additionalclarity. In such a configuration, the end 31 of the circuit board 30could be fixed within a recess 27 of the end cap 26 or otherwise fixed,such as by glue, to the end cap 26. In yet another embodiment, thecircuit board 30 could be a flexible circuit board in the form of a thinpiece of Mylar or similar material, either laid on a mounting surface orarranged in a housing portion.

Additional support for the light emitting diodes and the circuit boardmay be provided in the embodiment of FIG. 11 or any other embodiment bycoating the board, such as, for example, potting the board 30 by fillingin the empty space around the board 30 or part of the board 30 with anyknown transparent, translucent or tinted material such as is shown inFIG. 12. A conformal coating comprising a resin or other known materialscould be used. By example, FIG. 12 shows a light source according to theinvention in the form of a light bulb. The light bulb includes a housingportion 25 in the form of a conventional incandescent light bulb portionwith a conventional Edison screw connector 29 and a ballast 33. Theconnector 29 would screw into a conventional base. The ballast 33 canbe, for example, the ballast of a conventional self-ballasted compactfluorescent light bulb, or it could be merely an enclosure toincorporate control electronics as discussed in more detail herein. Theballast 33 could also be omitted with certain designs of the controlelectronics where the electronics would be incorporated into the housingportion 25, the connector 29 or the base (not shown). A circuit board 30coupled to the ballast 33 extends from the ballast 33 into the housingportion 25. A plurality of LEDs 22 is mounted on opposing sides of thecircuit board 30. The space between the circuit board 30 and the LEDs 22and the housing portion 25 is filled with slightly tinted material 23.In some cases, as where the material 23 is tinted, the potting material23 can provide the benefit of making the light from the discrete LEDs 22more diffuse.

The use of the potting material 23 with the embodiment according to FIG.1 is shown in the cross-sectional view of FIG. 13. It is worth notingthat, as can be seen by reference to FIGS. 11-13, the glass, plastic orthe like that normally forms a housing portion 24, 25 can be omitted. Incontrolled environments, the circuit board 30 and LEDs 22 can be leftunprotected. An alternative is to form the housing portion using acoating material such as the potting material 23 or a conformal coatingmolded over the LEDs 22 and circuit board 30. Particularly advantageouscan be the use of potting material 23 as shown in FIGS. 12 and 13 wherethe potting material 23 forms a shape at least partially in the form ofa conventional bulb. FIG. 12 shoes the potting material 12 shaped in asa conventional incandescent bulb and surrounded by a glass, plastic,etc. housing portion 25. If that housing portion 25 is omitted, thepotting material 12 would form a housing portion for the light source.FIG. 13 shows the potting material 23 forming a shape that partiallyconforms to a conventional tube that would, if the part identified asthe housing portion 24 were omitted, form the housing portion. Withrespect to FIG. 13, the potting material 23 could alternatively bemolded around the entire circuit board 30 to complete the shape of theconventional tube and serve as the housing portion, which would simplifythe couplings to the connectors 26, 28. As another option, the shape ofthe potting compound can act as a lens to affect the light distributionfrom the light source. This property can be used to optimize the lightdistribution for a particular application.

Within the scope of the present invention, light sources such as thelight tube 20 may be powered by current supplied by one of at least fourpower supply circuits 100, 200, 300, and 400. A first power supplycircuit includes a power source and any conventional fluorescent ballastused to power a conventional fluorescent tube. This may include ironballasts, high-frequency switchmode ballasts or other ballasttechnologies. A second power supply circuit includes a power source anda rectifier/filter circuit and eliminates the ballast. A third powersupply circuit includes a DC power source and a PWM (Pulse WidthModulation) circuit. A fourth power supply circuit powers the lightsources inductively.

In the embodiments presented, the power conditioning circuits are shownas a rectifier/filter circuit coupled to a PWM switch circuit, which iscoupled to a current-limiting circuit. They constitute a particulartopology for a switching power supply as an example, and the inventionis not intended to be limited thereby. One skilled in the art, providedwith the teachings and goals herein, would know how to modify thetopology from that described herein.

FIG. 5 is an electrical block diagram of a first power supply circuit100 for supplying current to the light sources. The first power supplycircuit 100 is particularly adapted to operate within an existing,conventional fluorescent lighting system that incorporates a ballast.Using the light tube 20 as an example, the first power supply circuit100 includes a conventional fluorescent light tube socket 40 having twoelectrical female connectors 42 disposed at opposite ends of the socket.Accordingly, a light tube 20 particularly adapted for use with the firstpower supply circuit 100 includes two end caps 26 and 28, each end caphaving the form of an electrical male connector 44 which mates with acorresponding electrical female connector 42 in the socket 40.

The first power supply circuit 100 also includes a power source 46 and aconventional magnetic or electronic fluorescent ballast 48. The powersource 46 supplies power from the conventional fluorescent ballast 48through the connectors for the light source such as the connectors 40,42.

The first power supply circuit 100 further includes a rectifier/filtercircuit 50, a PWM circuit 52, and one or more current-limiting circuits54. In this example, the rectifier/filter circuit 50, the PWM circuit52, and the one or more current-limiting circuits 54 of the first powersupply circuit 100 are packaged inside one of the two end caps 26 or 28of the light tube 20. The electronics described could be mounted withthe ballast 33, 48, or could alternatively be mounted on the circuitboard 30.

The rectifier/filter circuit 50 receives AC power from the ballast 48and converts the AC power to DC power. The PWM circuit 52 receives theDC power from the rectifier/filter circuit 50 and pulse-width modulatesthe DC power to the one or more current-limiting circuits 54. In apreferred embodiment of the present invention, the PWM circuit 52receives the DC power from the rectifier/filter circuit 50 andcyclically switches the DC power on and off to the one or morecurrent-limiting circuits 54. The DC power is switched on and off by thePWM circuit 52 at a frequency which causes the white light emitted fromthe LEDs 22 to appear, when viewed with a “naked” human eye, to shinecontinuously. The PWM duty cycle can be adjusted or varied by controlcircuitry (not shown) to maintain the power consumption of the LEDs 22at safe levels.

The DC power is modulated for several reasons. First, the DC power ismodulated to adjust the brightness or intensity of the white lightemitted from the LEDs 22 and, in turn, adjust the brightness orintensity of the white light emitted from the light source, here lighttube 20. Optionally, the brightness or intensity of the white lightemitted from the light source may be adjusted by a user. Second, the DCpower is modulated to regulate the intensity of light emitted from thelight source to compensate for supply voltage fluctuations, ambienttemperature changes, and other such factors that affect the intensity ofwhite light emitted by the LEDs 22. Third, the DC power is modulated toraise the variations of the frequency of light above the nominalvariation of 120 to 100 Hz thereby reducing illumination artifactscaused by low frequency light variations, including interactions withvideo screens. Fourth, the DC power may optionally be modulated toprovide an alarm function wherein light from the light source cyclicallyflashes on and off.

The one or more current-limiting circuits 54 receive the pulse-widthmodulated or switched DC power from the PWM circuit 52 and transmit aregulated amount of power to one or more arrays of LEDs 22. Eachcurrent-limiting circuit 54 powers a bank of one or more white LEDs 22.If a bank of LEDs 22 consists of more than one LED, the LEDs areelectrically connected in series in an anode to cathode arrangement. Ifbrightness or intensity variation between the LEDs 22 can be tolerated,the LEDs can be electrically connected in parallel.

The one or more current-limiting circuits 54 may include (1) a resistor,(2) a current-limiting semiconductor circuit, or (3) a switching powersupply-type current limiter. Note that while it is desirable to includesuch circuits 54, in some circumstances the necessary current-limitingfunction may be performed by the inherent electrical characteristics ofthe fluorescent ballast 48 and/or the inherent electrical resistance ofthe LEDs 22.

FIG. 6 is an electrical schematic of a switching power supply-typecurrent limiter 56. The limiter 56 includes an inductor 58, electricallyconnected in series between the PWM circuit 52 and the array of LEDs 22,and a power diode 60, electrically connected between ground 62 and a PWMcircuit/inductor node 64. The diode 60 is designed to begin conductionafter the PWM circuit 52 is switched off. In this case, the value of theinductor 58 is adjusted in conjunction with the PWM duty cycle toprovide the benefits described above. The switching power supply-typecurrent limiter 56 provides higher power efficiency than the other typesof current-limiting circuits listed above.

FIG. 7 is an electrical block diagram of a second power supply circuit200 for supplying current to a light source according to the presentinvention. By example, the second power supply circuit 200 includes aconventional fluorescent light tube socket 40 having two electricalfemale connectors 42 disposed at opposite ends of the socket 40.Accordingly, a light tube 20 particularly adapted for use with thesecond power supply circuit 200 would include two end caps 26 and 28,each end cap having the form of an electrical male connector 44, whichmates with a corresponding electrical female connector 42 in the socket40.

In the second power supply circuit 200, the power source 46 suppliespower directly to the rectifier/filter circuit 50 through connectors,end caps 26, 28 or base 29. The rectifier/filter circuit 50, the PWMcircuit 52, and the one or more current-limiting circuits 54 operate asdescribed above to power the one or more arrays of LEDs 22. Therectifier/filter circuit 50, the PWM circuit 52, and the one or morecurrent-limiting circuits 54 of the second power supply circuit 200 arepreferably packaged inside the connectors, end caps 26, 28 or base 29,or the housing portion 24, 25 of the light source or inside the lightsocket(s) corresponding to the one or more connectors. Thisconfiguration has the benefit of eliminating the conventional ballast 48from the circuit, allowing direct powering of the light source from astandard building or vehicle power supply. This allows improvedefficiency and reduced maintenance cost over the conventionalfluorescent system.

FIG. 8 is an electrical block diagram of a third power supply circuit300 for supplying current to a light source according to the presentinvention. Similar to the first and second power supply circuits 100 and200, the third power supply circuit 300 can include a conventionalfluorescent light tube socket 40 having two electrical female connectors42 disposed at opposite ends of the socket 40. Accordingly, a light tube20 particularly adapted for use with the third power supply circuit 300would include two end caps 26 and 28, each end cap having the form of anelectrical male connector 44, which mates with a correspondingelectrical female connector 42 in the socket 40.

The third power supply circuit 300 includes a DC power source 66, suchas a vehicle battery. In the third power supply circuit 300, the DCpower source 66 supplies DC power directly to the PWM circuit 52. ThePWM circuit 52 and the one or more current-limiting circuits 54 operateas described above to power the one or more arrays of LEDs 22. In thethird power supply circuit 300, the PWM circuit 52 is preferablypackaged in physical location typically occupied by a ballast 33, 48while the one or more current-limiting circuits 54 and LEDs 22 arepreferably packaged inside a connector, either one of the two end caps26 or 28 or the connector 29, or the housing portion 24, 25.

FIG. 9 is a fragmentary, perspective view of another embodiment of thepresent invention showing one end of the light tube 20 disconnected fromone end of the light tube socket 40. In this embodiment of the presentinvention, the light tube socket 40 includes a pair of brackets 68 andthe light tube 20 includes a pair of end caps 26 and 28 which mate withthe brackets 68.

FIG. 10 is an electrical block diagram of a fourth power supply circuit400 for supplying current to the light sources. Unlike the first,second, and third power supply circuits 100, 200, and 300, which arepowered through direct electrical male and female connectors 44 and 42,the fourth power supply circuit 400 is powered inductively. As such, thefourth power supply circuit 400 includes a light tube socket 40 havingtwo brackets 68 disposed at opposite ends of the socket 40 as shown inFIG. 9. At least one bracket 68 includes an inductive transmitter 70.Accordingly, a light tube 20 particularly adapted for use with thefourth power supply circuit 400 has two end caps 26 and 28 with at leastone end cap including an inductive receiver or antenna 72. When thelight tube 20 is mounted in the light tube socket 40, the at least oneinductive receiver 72 in the light tube 20 is disposed adjacent to theat least one inductive transmitter 70 in the light tube socket 40.

The fourth power supply circuit 400 includes the power source 46 whichsupplies power to the at least one inductive transmitter 70 in the lighttube socket 40. The at least one transmitter 70 inductively suppliespower to the at least one receiver 72 in one of the end caps 26 and/or28 of the light tube 20. The at least one inductive receiver 72 suppliespower to the rectifier/filter circuit 50. The rectifier/filter circuit50, PWM circuit 52, and the one or more current-limiting circuits 54operate as described above to power the one or more arrays of LEDs 22.In this manner, the light tube 20 is powered without a direct electricalconnection.

The LEDs shown in drawing FIGS. 1-3, 12 and 13 are the common discretecomponents. However, the invention is not limited to these discretecomponents. For example, surface-mounted light-emitting diodes that omitthe familiar bulb portion are also possible. Another option is theorganic LED, which is formed of semiconducting organic polymers layerssandwiched between two conductors. In the instant invention, a singleorganic LED (OLED), which comprises varying numbers of arrays printed ona substrate, can be made in the form of a sheet such as the rigid OLEDsheet 35 shown in FIG. 14. The sheet 35 can be installed on or in placeon the circuit boards described herein. An organic LED can also beformed on substrates comprising thin metal foils or flexible plastics.In this case, the organic LED is itself flexible and can be installedsuch that it is surrounded by a housing portion, such as housing portion24 of light tube 20 by rolling a sheet comprising a flexible organic LED37 and allowing it to form the shape of the housing portion 24 as shownin FIG. 15. Of course, in embodiments incorporating the organic LED, thehousing portion can still be formed in whole or in part by a coatingmaterial such as the potting material 23 or the conforming layer.

What is claimed is:
 1. A light source comprising: a housing; a connectorconfigured for connection to an electrical socket and coupled to an endof the housing; at least one organic light emitting diode sheet mountedinside the housing and in electrical communication with the connector;and a power supply circuit for supplying electrical current to the atleast one organic light emitting diode through the connector.
 2. Thelight source of claim 1 wherein the at least one organic light emittingdiode sheet is at least one flexible sheet arranged into a curved shapedwithin the housing.
 3. The light source of claim 2 wherein the at leastone flexible sheet is a single organic light emitting diode sheet. 4.The light source of claim 1 wherein the connector comprises a firstbi-pin electrical connector shaped to be coupled with a fluorescentlight tube socket, the light source further comprising: a second bi-pinelectrical connector disposed at an opposing end of the circuit boardfrom the first bi-pin electrical connector, the second bi-pin electricalconnector shaped to be coupled with a fluorescent light tube socket. 5.The light source of claim 1, further comprising: a circuit board inelectrical communication with the connector, the at least one organiclight emitting diode sheet mounted in electrical communication with thecircuit board.
 6. The light source of claim 5 wherein the power supplycircuit is mounted on the circuit board.
 7. The light source of claim 1wherein the power supply circuit comprises a rectifier for converting ACto DC power and a modulating circuit for modulating the DC power.
 8. Thelight source of claim 1 wherein the at least one organic sheet is incontact with at least a portion of the housing and surrounded by atleast a portion of the housing.
 9. The light source of claim 8 whereinthe power supply circuit comprises a rectifier for converting AC to DCpower, at least one current-limiting circuit and means for modulatingthe DC power.
 10. The light source of claim 9 wherein the connectorcomprises a first bi-pin electrical connector shaped to be coupled witha fluorescent light tube socket and wherein the housing portion issubstantially tubular, the light source further comprising: a secondbi-pin electrical connector disposed at an opposing end of the hollowtube from the first bi-pin electrical connector, the second bi-pinelectrical connector shaped to be coupled with a fluorescent light tubesocket.
 11. The light source of claim 1 wherein the housing comprises apotting material and wherein the potting material is one of clear andtinted.
 12. The light source of claim 1 wherein the housing comprises arigid hollow structure including at least one of glass and plastic. 13.The light source of claim 1, further comprising: a circuit board inelectrical communication with the connector, the at least one organiclight emitting diode sheet mounted in electrical communication with thecircuit board; and a heat sink extending from the circuit board todissipate heat.
 14. The light source of claim 13 wherein the heat sinkis integral with the circuit board.